<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
  </head>
  <body>
    <script>
      // console.log(a)
      // let a = 'lalal'
      // console.log(a);
      
      function fn(){
        // console.log(a);
        let a = 'dog'
        console.log(a);
      }

      fn()

      const b = 'dog';
      //b = 'cat';
      console.log(b)

      const arr = ['cat', 'dog', 'elephant']
      // arr = ['1', '2', '3']
      arr[0] = 'snake'
      console.log(arr)

      const obj = {
        id: '1',
        name: 'dog',
        age: 3
      }
      obj.age = 2
      console.log(obj)
    </script>
  </body>
</html>
